It is well known that internal combustion engines may be operated by many different fuels other than gasoline which presently is the major fuel for such engines. Other fuels, such as ethanol, also known as ethyl alcohol, methanol, butane and others may also be used. However, since most internal combustion engines and their carburetors are designed for efficient use of gasoline, other fuels cannot be effectively used without changes, either in the engine or its carburetor. Such changes are necessary because there exists for each fuel a particular air/fuel ratio for most efficient combustion. This chemically correct ratio of air to fuel is known as the stoichiometric ratio. As an example, the stoichiometric ratio of gasoline is 14.96 units air to 1 unit of fuel; for ethyl alcohol, also known as ethanol, the ratio is 9.01 units of air to 1 unit of ethanol and for methyl alcohol, also called methanol, 6.47 units of air to 1 unit of methanol. With these relatively wide differences in the stoichiometric ratios, it is evident that an internal combustion engine and its carburetor designed for one fuel cannot, without substantial change, operate on other fuels having substantially different air/fuel ratios.
The problem of using multiple or different fuels in the engine designed to be operated by gasoline is further complicated by the type of carburetor which is generally used with such engines. This carburetor is a Venturi type, and includes the well known venturi tube arrangement. In such structure, the suction developed by the flow of air through the venturi is depended upon to draw the gasoline or other liquid fuel, which is at atmospheric pressure, into the venturi to mix with the air and form the combustible mixture. Therefore, the air/fuel ratio in the most widely used carburetor for internal combustion engines is controlled by the suction developed in the venturi. The gasoline is at atmospheric pressure and does not control the air/fuel ratio.
In view of the foregoing, it becomes evident that an internal combustion engine designed to operate on gasoline and having a Venturi type carburetor cannot efficiently operate on other liquid fuels such as alcohol.
In recent years, the several shortages and the increased cost of hydrocarbon fuels, such as gasoline have caused a greater interest in the use of alcohol fuels, such as ethanol and methanol in internal combustion engines. The availability of ethanol which can be made in significant quantities from a variety of raw materials and its excellent operating characteristics in spark ignition internal combustion engines makes it attractive to the public and particularly to the farming community, which presently produces the grain and other raw materials from which ethanol or alcohol is made.
There is a general recognition that alcohol fuels are advantageous and conversion kits, which convert spark ignition internal combustion engines to enable them to operate on alcohol are appearing in the U.S. market (See Mart Kirik publication prepared for the Canadian National Power Alcohol Conference June 19-20, 1980 Fort Garry Hoten, Winnepeg, Manitoba, Canada). A publication by Professor John G. Mingle, of Oregon State University dated October 1979 compares the fuel properties of gasoline, methanol and ethanol and points out the advantages of alcohol fuels for internal combustion engines. The publication by David Vizard in "Popular Hot Rodding" magazine, April 1980 outlines the changes which are required to adapt the internal combustion racing engine and its carburetor to alcohol use.
The ideal modification would be to design the engine and its carburetor to operate efficiently on multiple fuels but because of the wide differences between the air/fuel ratios required for efficient operation of the engine with the various fuels, no one, to applicant's knowledge has been able to accomplish this.
All of the suggested conversions of internal combustion engines for alcohol use are directed to modification or changes either in the engine or in the carburetor, which changes adapt the engine to operate only on alcohol. Because the engine converted to operate on alcohol has difficulty in starting at lower ambient temperatures, a small volume of gasoline for start-up is sometimes used. However, because the modifications which are made in the engine or the carburetor are directed to the use of alcohol fuel, the engine cannot operate normally and efficiently on gasoline over any extended time period. Therefore, as a practical matter, the conversions which are described in the prior art provide an internal combustion engine which is capable of efficiently operating only on one fuel, such as alcohol.